1. Field of the Invention
The present invention is generally related to stimulating nerves and body parts. More specifically, the present invention is related to nerve stimulation devices used for stimulating target nerves and body parts to achieve therapeutic results.
2. Description of the Related Art
There are a wide variety of medical conditions that may affect an individual's health and well-being, and many treatment options have been developed to help physicians treat such conditions. While the number of treatment options has increased, such options are often merely palliative, i.e., relieving symptoms rather than actually curing the underlying condition. In fact, treatment protocols effectively targeting the underlying cause of a condition are quite rare.
A common medical condition is obesity, which often results from an imbalance between food intake and energy expenditure. Severe weight loss and abnormal loss of appetite is an equally serious condition that can lead to suffering and death. The most familiar example is anorexia nervosa, a condition that classically affects young women and is associated with pathologic alterations of hypothalamic and pituitary gland function.
Another adverse medical condition is fecal incontinence, which involves the loss of voluntary control to retain feces in the rectum. Fecal incontinence may result from a number of causes, such as old age, disease or trauma. Still another condition is urinary incontinence. One type of urinary incontinence is urge incontinence, which appears to be neurologically based and generally revealed as detrusor muscle instability or “bladder spasms.”
A wide variety of therapies exist for treating the above medical conditions. One therapy involves behavior modification such as reducing food intake and increasing exercise. Another option involves using pharmacologic agents, for example to control appetite and increase energy expenditure. A third option involves surgery such as gastric bypass surgery and gastric banding. Although these treatment options may be very effective in treating one or more of the above-described conditions, they may be highly invasive, require significant lifestyle changes, and result in severe complications.
There have been a number of attempts to treat the above conditions using transcutaneous electrical nerve stimulation systems, commonly referred to as TENS. TENS devices are extremely invasive because they have electrode leads that must be implanted inside a patient, in close proximity to a target nerve (e.g. a sacral nerve). Another disadvantage with TENS is a limitation on the depth to which a low frequency stimulation signal (such as those needed to stimulate the pudendal and/or sacral nerves) can be driven due to tissue impedance and resulting signal dissipation, and without causing significant discomfort to a patient. Still another disadvantage with TENS is the limited effectiveness of higher frequency signals in stimulating nerves. As a result, TENS devices are unable to achieve deep nerve stimulation without the application of current intensities that are too high to be tolerated by patients for extended periods of time, if at all. For these reasons, despite the availability of TENS for well over 25 years, there has yet to be a commercially successful application of TENS for deeper nerve stimulation.
In some nerve stimulation devices, it has been observed that the generated electric field spreads widely, affecting untargeted muscles and nerves along with the target nerve. The wide spreading of the electric field significantly reduces the strength of the electrical signal at the target nerve. In order to properly stimulate the target nerve, the strength of the electrical signal must be substantially increased. This requires the devices to draw more power from the battery.
In other nerve stimulation devices, it has been observed that tissue impedance prevents the generated electric field from passing deeply into the tissue. As a result, the generated electric field is able to penetrate only the top layers of the epidermis, and is unable to pass deeply into the tissue to stimulate nerves located deeper in the tissue.
Thus, there remains a need for improved devices and methods of stimulating body parts and nerves. In particular, there remains a need for improved nerve stimulation devices that effectively stimulate target nerves and body parts, while not stimulating untargeted nerves and body parts. Furthermore, there remains a need for nerve stimulation devices that are less invasive, and that require less power to operate effectively, thereby minimizing the need to replace and/or recharge power sources. There also remains a need for nerve stimulation devices that are capable of stimulating nerves located deeper within body tissue, while minimizing power and size requirements. In addition, there remains a need for devices and methods that are able to effectively stimulate nerves using less power.